Handbook:HPPA/Blocks/Disks

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Partitions and slices

Although it is theoretically possible to use a full disk to house the Linux system, this is almost never done in practice. Instead, full disk block devices are split up in smaller, more manageable block devices. On most systems, these are called partitions. Other architectures use a similar technique, called slices.

Designing a partition scheme

How many partitions and how big?

The number of partitions is highly dependent on the environment. For instance, if there are lots of users, then it is advised to have /home/ separate as it increases security and makes backups easier. If Gentoo is being installed to perform as a mail server, then /var/ should be separate as all mails are stored inside /var/. A good choice of filesystem will then maximize the performance. Game servers will have a separate /opt/ as most gaming servers are installed there. The reason is similar for the /home/ directory: security and backups. In most situations, /usr/ is to be kept big: not only will it contain the majority of applications, it typically also hosts the Gentoo ebuild repository (by default located at /var/db/repos/gentoo) which already takes around 650 MiB. This disk space estimate excludes the binpkgs/ and distfiles/ directories that are stored under /var/cache/ by default.

It very much depends on what the administrator wants to achieve. Separate partitions or volumes have the following advantages:

  • Choose the best performing filesystem for each partition or volume.
  • The entire system cannot run out of free space if one defunct tool is continuously writing files to a partition or volume.
  • If necessary, file system checks are reduced in time, as multiple checks can be done in parallel (although this advantage is more with multiple disks than it is with multiple partitions).
  • Security can be enhanced by mounting some partitions or volumes read-only, nosuid (setuid bits are ignored), noexec (executable bits are ignored), etc.

However, multiple partitions have disadvantages as well. If not configured properly, the system might have lots of free space on one partition and none on another. Another nuisance is that separate partitions - especially for important mount points like /usr/ or /var/ - often require the administrator to boot with an initramfs to mount the partition before other boot scripts start. This isn't always the case though, so results may vary.

There is also a 15-partition limit for SCSI and SATA unless the disk uses GPT labels.

What about swap space?

There is no perfect value for the swap partition. The purpose of swap space is to provide disk storage to the kernel when internal memory (RAM) is under pressure. A swap space allows for the kernel to move memory pages that are not likely to be accessed soon to disk (swap or page-out), freeing memory. Of course, if that memory is suddenly needed, these pages need to be put back in memory (page-in) which will take a while (as disks are very slow compared to internal memory).

When the system is not going to run memory intensive applications or the system has lots of memory available, then it probably does not need much swap space. However, swap space is also used to store the entire memory in case of hibernation. If the system is going to need hibernation, then a bigger swap space is necessary, often at least the amount of memory installed in the system.


Using fdisk on HPPA

Use fdisk to create the partitions needed:

root #fdisk /dev/sda

HPPA machines use the PC standard DOS partition tables. To create a new DOS partition table press the o key.

Command (m for help):o
Building a new DOS disklabel.

PALO (the HPPA bootloader) needs a special partition to work. A partition of at least 16 MB at the beginning of the disk needs to be created for it. The partition type must be of type f0 (Linux/PA-RISC boot).

Important
If this is forgotten and the installation continues without a special PALO partition, then eventually the system will fail to restart. Also, if the disk is larger than 2 GB, make sure that the boot partition is in the first 2 GB of the disk. PALO is unable to read a kernel after the 2 GB limit.
FILE /etc/fstabA simple default partition scheme
/dev/sda2    /boot   ext2    noauto,noatime   1 1
/dev/sda3    none    swap    sw               0 0
/dev/sda4    /       ext4    noatime          0 0

In fdisk, such a partition layout looks like so:

Command (m for help):p
Disk /dev/sda: 4294 MB, 4294816768 bytes
133 heads, 62 sectors/track, 1017 cylinders
Units = cylinders of 8246 * 512 = 4221952 bytes
  
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1           8       32953   f0  Linux/PA-RISC boot
/dev/sda2               9          20       49476   83  Linux
/dev/sda3              21          70      206150   82  Linux swap
/dev/sda4              71        1017     3904481   83  Linux